TW202106082A - Method for voice calls and mobile termination - Google Patents

Abstract

Methods and apparatus are provided for EPS fallback status report by the modem to the upper layers. In one embodiment, the mobile terminal (MT) initiates a 5G voice call, detects an EPSFB triggered by the wireless network, identifies one or more EPSFB status and sends one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB status. In one embodiment, the EPS fall back is a redirection procedure. In another embodiment, the EPS fallback is a handover procedure. In yet another embodiment, the one or more EPSFB status indictors comprising a redirection to EPS started indicator, a handover to EPS started indicator, a redirection to EPS failed indicator, a handover to EPS failed indicator, a redirection to EPS success indicator, and a handover to EPS success indicator. In one embodiment, the MT sends EPSFB status indicators using AT command.

Description

Voice calling method and mobile terminal

The present disclosure relates generally to wireless communication, and more specifically, to modem and application interaction for voice calls.

Wireless cellular communication networks have grown exponentially over the years. The fifth-generation system (5GS) has been developed to meet the growing demand for wireless services. 5GS provides higher-speed data services. In the 5G era, voice services and their development and evolution are also key elements in the evolution of wireless networks. 5GS uses new radio (NR) access technology. 5GS provides voice over NR (voice over NR, VoNR) for voice services. 5G will also continue to use 4G voice architecture and IP multimedia subsystem (IP multimedia subsystem, IMS) to provide voice services. For 4G wireless access, we have an LTE network and its voice service VoLTE.

Some 5GS networks provide VoPS on 3GPP through EPS fallback (EPSFB) through evolved packet system (EPS). When the UE initiates an IMS voice call on these networks, the 5GS network will initiate the EPS fallback process for the UE, and the UE cannot control it. If EPSFB fails for some reason, the UE can stay on NR 5GS. The UE, especially the upper layer of the UE, does not know that it has tried to perform EPSFB and has failed. Similarly, if the EPSFB is successful and the UE is connected to the LTE 4G network but cannot establish a voice call, the UE, especially the upper layer of the UE, does not know the EPSFB status. Generally, if EPSFB fails or the call itself fails after EPSFB, the upper layer of the UE (for example: the application that controls the call) decides in which domain to retry the call. In order to take the most appropriate measures after the EPSFB fails, it will be beneficial for the upper layer to obtain an indication of whether the EPSFB has failed or succeeded and other EPSFB status information. Currently, there is no EPSFB information available for the upper layer of the UE.

A solution is needed to enable the upper layer of the UE to obtain EPSFB status information.

In view of this, the present disclosure proposes a voice call method and mobile terminal to solve the above-mentioned problems.

According to one embodiment, a voice call method is provided. The method includes initiating a 5G voice call in a wireless network by a mobile terminal; detecting an evolved packet system fallback (EPSFB) triggered by the wireless network; identifying one or more EPSFB states; and according to the identified one Or multiple EPSFB statuses, one or more EPSFB status indicators are sent to at least one upper layer. In one embodiment, EPS fallback is a redirection process or a handover process. In yet another embodiment, the one or more EPSFB status indicators include redirect to EPS start indicator, switch to EPS start indicator, redirect to EPS failure indicator, switch to EPS failure indicator, redirect to EPS success indicator, and switching to EPS success indicator.

According to one embodiment, a mobile terminal is provided. The mobile terminal includes a network interface circuit, a detector circuit, a status circuit, and an upper layer circuit. The network interface circuit is used to initiate 5G voice calls in the wireless network; the detector circuit is used to detect the evolved packet system fallback (EPSFB) triggered by the wireless network; the state circuit is used to identify one or more EPSFB states And the upper layer circuit is used to send one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB statuses.

In the present invention, the upper layer EPSFB state is provided, and appropriate measures can be taken after the EPSFB fails, so that the UE can decide in which domain to retry the call or initiate the call.

These and other objects of the present invention will undoubtedly become apparent to those skilled in the art after reading the following detailed description of the preferred embodiments shown in the various drawings and drawings.

In the specification and the scope of patent application, certain words are used to refer to specific elements. Those skilled in the art should understand that electronic device manufacturers may use different terms to refer to the same component. This specification and the scope of the patent application do not use differences in names as ways to distinguish elements, but use differences in functions of elements as the basis for distinction. The "including" mentioned in the entire specification and the scope of the patent application is an open term, so it should be interpreted as "including but not limited to". In addition, the term "coupled" herein includes any direct and indirect electrical connection means. Therefore, if it is described that the first device is electrically connected to the second device, it means that the first device can be directly connected to the second device, or indirectly connected to the second device through other devices or connection means.

Figure 1 illustrates an exemplary wireless network 100 and user equipment (UE) according to a novel aspect. The wireless network 100 includes a 5GS network with an exemplary base station gNB 102 and an exemplary 5G core (5G core, 5GC) 106, and an exemplary base station eNB 101 and an exemplary evolved packet core (EPC) 107 4G/LTE network. The mobile stations/UEs 103 and 104 are connected to the wireless network 100. The UE 104 is served by the eNB 101 through the uplink 111 and the downlink 112. The UE 103 is served by the gNB 102. When the UE 103 is configured with dual connectivity, the UE 103 is served by the eNB 101 through the uplink 116 and the downlink 117. At the same time, the UE 103 is also served by the gNB 102 through the uplink 113 and the downlink 114. The eNB 101 and the gNB 102 communicate through a link 115. 5GS supports IMS registration locally but does not support voice services (Voice over NR). If both the UE and the network support EPS voice, 5GS can choose to use the voice call on EPS. When the 5GS network triggers a fallback to the EPS or the 5GS network is willing to direct the voice call to the EPS, EPSFB for the voice call may occur. EPSFB may occur both for calls initiated by the mobile station and calls terminated by the mobile station. When the UE 103 initiates an IMS voice call to the IMS network 108, the 5GS network can initiate an EPS fallback process. EPSFB is controlled and triggered by the network. Generally, the UE cannot control EPSFB and cannot recognize when EPSFB occurs. In a novel aspect, the mobile terminal part of the UE detects the EPSFB status and sends it to the upper layer of the UE.

Figure 1 further illustrates a simplified block diagram of UE 103, gNB 102, and eNB 101. The UE 103 has an antenna 136 for transmitting and receiving radio signals. The RF transceiver module 137 coupled to the antenna 136 receives the RF signal from the antenna 136, converts it into a baseband signal, and sends it to the processor 132. The RF transceiver 137 also converts the baseband signal received from the processor 132, converts it into an RF signal, and transmits and outputs to the antenna 136. In one embodiment, the RF transceiver module 137 has two transceivers, Transceiver-1 133 and Transceiver-2 135. The processor 132 processes the received baseband signal and invokes different functional modules to perform functions in the UE 103. The memory 131 stores program instructions and data 138 to control the operation of the UE 103.

For external applications, EPSFB status can be provided through AT commands. AT commands are used to control mobile terminal (Mobile Termination, MT) functions and network services from terminal equipment (Terminal Equipment, TE) through a terminal adaptor (Terminal Adaptor, TA). As an example, the UE 103 includes TE, TA, and MT. TE can use AT commands to control MT to obtain EPSFB status information. According to a novel aspect, a new AT command interface (interface) is proposed to report EPSFB status to TE. After being enabled, MT can automatically provide EPSFB status information to TE. TE can also query the status of EPSFB through AT commands. The EPSFB status report can also be disabled by AT command.

The UE 103 also includes multiple modules that perform different tasks according to embodiments of the current invention. The mobile terminal (MT) 191 initiates a 5G voice call in the wireless network 100, detects the evolved packet system (EPS) fallback (EPSFB) triggered by the IMS 108, identifies one or more EPSFB states, and based on the identified one or The multiple EPSFB statuses send one or more EPSFB status indicators to at least one upper layer. The terminal equipment (TE) 192 receives the EPSFB status from the MT 191 and determines the voice call status of the UE 103. The EPSFB status module 193 processes EPSFB status information. The EPSFB status module 193 may be a part of the MT 191 or a part of the TE 192 or an independent module. The UE module can be implemented in software, firmware, or hardware/circuitry. In another embodiment, the EPSFB status module 193 may distribute its functions in both the MT 191 and the TE 192.

Also shown in Figure 1 is an exemplary block diagram of the eNB 101. The eNB 101 has an antenna 156 for transmitting and receiving radio signals. The RF transceiver module 153 coupled to the antenna receives the RF signal from the antenna 156, converts it into a baseband signal, and sends it to the processor 152. The RF transceiver 153 also converts the baseband signal received from the processor 152 into an RF signal, and transmits and outputs to the antenna 156. The processor 152 processes the received baseband signals, and calls different functional modules to perform functions in the eNB 101. The memory 151 stores program instructions and data 154 to control the operation of the eNB 101. The eNB 101 also includes multiple functional modules for performing different tasks according to the embodiments of the present invention. The EPSFB module 155 processes the communication with the UE 103 and executes the EPSFB process.

Figure 1 also shows an exemplary block diagram of the gNB 102. The gNB 102 has an antenna 126 for transmitting and receiving radio signals. The RF transceiver module 123 coupled to the antenna receives the RF signal from the antenna 126, converts it into a baseband signal, and sends it to the processor 122. The RF transceiver 123 also converts the baseband signal received from the processor 122, converts it into an RF signal, and transmits and outputs to the antenna 126. The processor 122 processes the received baseband signal and calls different functional modules to execute the functions in the gNB 102. The memory 121 stores program instructions and data 124 to control the operation of the gNB 102. The gNB102 also includes multiple functional modules to perform different tasks according to the embodiments of the present invention. The EPSFB module 125 handles the communication with the UE 103 and executes the EPSFB process.

In a novel aspect, the EPSFB status is indicated to the upper layer so that if the EPSFB fails, the upper layer can decide in which domain to retry the call. In one embodiment, the modem/mobile terminal (MT) provides the upper layer with indication information about the status of the EPSFB process.

Figure 2 illustrates an exemplary block diagram of a mobile terminal reporting EPSFB status according to an embodiment of the present invention. UE 201 is connected to the 5GS network. The UE 201 is connected to a 5G access station (access station)/gNB 202 and a 4G/LTE base station/eNB 203. The 5GS network also includes network entities 204 (including 5GC, EPC and IMS). In step 221, the UE 201 initiates a mobile originated (MO) or mobile terminated (MT) call, and then performs media set up (media set up). In step 221, the wireless network initiates the EPSFB process. In one embodiment, in step 222, the EPSFB process is performed through a redirection process. In the redirection process for the EPSFB case, the UE 201 releases the call with the 5G gNB 202 and re-establishes the link with the LTE/eNB 203, where a new radio connection is started for the VoLTE call. In one embodiment, the MT 211 recognizes the start of EPSFB via redirection by detecting a redirection command. In one embodiment, the redirection command is a "connection release command" with redirection information received on the NR during the MO/MT call process. In another embodiment, in step 223, the EPSFB process is performed through a handover process. During the handover process for the EPSFB case, the UE 201 performs handover from 5GC to EPC while maintaining the connection with the initial 5G gNB. In one embodiment, the MT 211 recognizes the start of the EPSFB via the handover by detecting the handover command indicating the start of the EPSFB process. In a novel aspect, the MT 211 of the UE 201 obtains EPSFB status information and sends the status information (EPSFBS) to one or more upper layers of the UE 201. In step 281, once the EPSFB starts, the MT 211 can obtain an EPSFB start indicator (EPSFB start indicator). In step 280, the EPSFB start indicator is sent to the upper layer 212 of the UE 201.

Once the network triggers the EPSFB through the redirection process or the handover process, it needs to indicate the status of the EPSFB to the upper layer of the UE. In step 231, the EPSFB process is successful. In step 282, the MT 211 obtains EPSFB success information, and in step 280, sends the EPSFB success indicator to the upper layer 212. In one embodiment, the MT can recognize that the EPSFB via the handover is successful by detecting that the handover is completed. In another embodiment, the MT can recognize that the EPSFB via redirection is successful by detecting that the UE is camped on an LTE cell. Similarly, if the EPSFB fails in step 232, the MT 211 obtains EPSFB failure information in step 283 and sends the EPSFB failure indicator to the upper layer 212 in step 280. In one embodiment, the MT recognizes the EPSFB failure by detecting the handover failure. In another embodiment, the MT recognizes EPSFB failure by detecting that the UE cannot find an LTE cell.

The MT 211 of the UE 201 is a modem of the UE 201. As shown in step 280, it provides an indication or a set of information about the status of the EPSFB process to the upper layer. When the application initiates an IMS call, the modem will provide EPSFB indicator to the application layer or upper layer, including the start indicator of redirecting to EPS, the start indicator of switching to EPS, the failure indicator of redirecting to EPS, and the indicator of switching to EPS. The failure indicator of EPS, the success indicator of redirecting to EPS, and the success indicator of switching to EPS. In one embodiment, the instruction to the application layer/upper layer can be provided through AT commands or related methods.

Figure 3 illustrates an example diagram of EPSFB for IMS voice when the EPSFB status indication is sent to the upper layer according to an embodiment of the present invention. UE 301 is connected to 5GS and LTE networks in a wireless network. The wireless network includes the next generation radio access network (NG-RAN) 302 that provides NR and LTE wireless access, the evolved UTRAN (E-TRAN) 303, and access mobility management functions ( access mobility management function (AMF) 304, mobility management entity (MME) 305, service gateway (SGW) 306, packet data network gateway (PGW)/session management Function (session management function, SMF)/user plane function (UPF) 307 and IMS 308. In step 311, the UE initiates an MO or MT IMS voice session in 5GS. In step 312, the network initiates a PDU (protocol data unit) session modification (session modification) to establish a QoS flow for IMS voice. In step 313, the 5GS radio access NG-RAN 302 triggers the EPSFB process. In one embodiment, the NG-RAN 302 also triggers a measurement report request (solicitation). In step 314, the 5GS network entity PGW/SMF/UPF 307 rejects the PDU session modification, indicates the ongoing IMS voice fallback, and sends the information to the NG-RAN 302. In step 315, the PGW/SMF-UPF 307 starts the redirection or handover to the EPS process and sends a signal to the UE 301.

In one embodiment, in step 321, when the modem of the UE 301 detects the EPSFB signal, it sends the EPSFB status indication information to the upper layer. EPSFB status indications include EPSFB start, EPSFB success, and EPSFB failure. In step 316, the network initiates a tracking area update (TAU) process. In step 326, the network attaches a PDN connection request whose request type is "handover". In step 317, the network initiates PDN connection modification to establish a dedicated bearer for voice. In step 318, the IMS voice session establishment is continued. In a novel aspect, the modem/mobile terminal recognizes the EPSFB triggered by the network. In one embodiment, when the redirection or handover process starts, the modem recognizes the event in step 315. In another novel aspect, the modem recognizes the status of EPS rollback triggered by the network, including EPSFB start, EPSFB success, and EPSFB failure. In another novel aspect, when an MT IMS call is established in step 311, in step 315, the UE should wait for a network redirection or handover command from NR to EPS to make this call on LTE.

The EPSFB status indication provided by the modem to the upper layer will enable the UE to decide in which domain to retry the call or initiate a call. In order to take the most appropriate measures after the EPSFB fails, it would be beneficial for the upper layer to obtain the EPSFB status indication. In one embodiment, the modem/mobile terminal provides the instruction to the application/upper layer (application/upper layer) through an AT command.

Figure 4 illustrates a simplified block diagram of the architecture of a user equipment UE 400 according to an embodiment of the present invention. The user equipment UE 400 includes a terminal device (TE 401) and a mobile terminal (MT 403) through a terminal adapter (TA 402) interface. . TA, MT, and TE can be implemented in the form of separate entities or integrated entities as required. The defined span of control of AT commands can handle any physical realization of the following structures: TA, MT, and TE as three independent entities; TA is integrated under the scope of MT, and TE is implemented as an independent entity; TA is integrated under the scope of TE, and MT is realized as an independent entity; TA and MT are integrated under the scope of TE as a single entity.

In the example in Figure 4, AT commands can be observed on the link between TE 401 and TA 402. However, most AT commands exchange information about MT, not information about TA. The interface between TE 401 and TA 402 operates through existing serial cables, infrared links, and all link types with similar behavior. The interface between TA 402 and MT 403 depends on the interference within MT 403. In one embodiment, the TE 401 sends an AT command to the TA 402, and the TA 402 converts it into MT control information to be sent to the MT 403. The AT command may be a read command (read command) used to obtain the EPSFB status from the MT 403 or may be a set command (set command) used to enable or disable automatic EPSFB status reporting for the MT 403. In response, the MT 403 sends the EPSFB status back to the TA 402, and the TA 402 converts it into a response to be sent to the TE 401. The response may include updated EPSFB status information.

Figure 5 illustrates an exemplary table of AT commands for EPSFB status according to an embodiment of the present invention. As shown in Figure 5, the AT+CEPSFB command is a set command or a read command or a test command. When <reporting> = 1, set the command to control the presentation of unsolicited result code + CEPSFB: <stat>, <type>, and there are changes due to the EPSFB process triggered by the network. The read command returns <reporting>, which indicates whether EPSFB status reporting is enabled or disabled. When reporting is enabled, the parameters <stat> and <type> indicate the status of the most recently received EPSFB. When reporting is disabled, EPSFB status will not be provided.

The defined values of related information include: • ＜reporting ＞: Integer type, ＜reporting ＞ = 0, the EPSFB status is disabled without request The requested result code, <reporting> =1, enable the unsolicited result generation of EPSFB status Code +CEPSFB: <n>, <stat>, <type>. • <stat>: Integer type, indicating EPSFB status. When MO/MT calls (not including VoNR) When performing on NR: O "0" The fallback from 5GS to EPS starts. ("Switch/Redirection Command" indicates that the EPS fallback process has started) O "1" The rollback from 5GS to EPS is successful. (Send "Handover complete" or "For redirection, UE camps on LTE cell") O "2" The fallback from 5GS to EPS failed. (Send "Handover failed" or "UE cannot find LTE cell") • ＜type＞: integer type; indicates the EPSFB type O 0: Handover. (Received on NR during MO/MT call (not including VoNR) To "Switch Command") O 1: Redirect. (During MO/MT calls (not including VoNR), on NR Received "connection release command with redirection information") This command can be applied to UEs that support 5GS.

Figure 6 illustrates a simplified block diagram of a terminal device (TE 600) with an application layer that receives EPSFB status from an MT according to an embodiment of the present invention. TE 600 includes processor 601, memory 602 and protocol stack 610. Protocol stack 610 includes application (APP) layer, transmission (TCP/UDP) layer, network (IP) layer, data link layer and physical (PHY) Layer and radio interface. The TE 600 further includes a system control module 620, which includes a user interface, a configuration and control module, a connection processor, and a congestion control processor. The processor 601 processes different applications and calls different system control modules to perform various functions of the TE 600. The memory 602 stores program instructions and data 603 to control the operation of the TE 600. System control modules and circuits can be implemented and configured to perform the functional tasks of TE 600. The TE 600 includes an application layer that receives EPSFB status information from the modem. In one example, the TE 600 sends an AT read command to obtain the EPSFB status from the modem. In another example, the TE 600 sends an AT set command to enable or disable the EPSFB status report option. Therefore, the TE 600 can determine whether EPSFB is applicable before sending subsequent EPSFB status-related requests and parameters.

Fig. 7 illustrates a simplified block diagram of a mobile terminal (MT 700) transmitting EPSFB status to an upper layer according to an embodiment of the present invention. The MT 700 has an antenna 706 for transmitting and receiving radio signals. The RF transceiver module 704 coupled to the antenna receives the RF signal from the antenna 706, converts it into a baseband signal, and sends it to the processor 701 through the baseband module (BB) 705. The RF transceiver 704 also converts the baseband signal received from the processor 701 into an RF signal through the baseband module 705, and then sends it to the antenna 706. The processor 701 processes the received baseband signal and calls different functional modules to execute the functions in the MT 700. The memory 702 stores program instructions and data 703 to control the operation of the MT 700.

The MT 700 also includes a set of protocol stacks 710 and a control circuit. The control circuit includes various system modules 720 for performing the functional tasks of the MT 700. The protocol stack 710 includes a non-access-stratum (Non-Access-Stratum, NAS), a radio resource control (Radio Resource Control, RRC) layer, and a packet data convergence protocol/radio link control (Packet Data Convergence Protocol/Radio Link Control, PDCP). / RLC) layer, Media Access Control (MAC) layer and physical (PHY) layer. The system module 720 includes a plurality of functional modules/circuits. The network interface circuit initiates 5G voice calls in the wireless network. The detector circuit detects the EPSFB triggered by the wireless network. The state circuit identifies one or more EPSFB states. The EPSFB reporting circuit sends one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB statuses.

In one embodiment, the MT 700 further includes a terminal adapter (TA 730), which receives and sends AT commands, and converts the AT commands to be processed by the processor 701 to control MT functions. In another embodiment, the TA may be located in the TE or as a separate entity. In one example, the TA 730 receives an AT read command from the TE to enable the MT to obtain the EPSFB status. In another example, the TA 730 receives an AT setting command for setting EPSFB status report options from the TE, so that the MT can detect the EPSFB status change and report the updated EPSFB applicability status information accordingly.

Fig. 8 illustrates an exemplary flowchart for the mobile terminal to detect the EPSFB status indication and send it to the upper layer according to an embodiment of the present invention. In step 801, the mobile terminal initiates a 5G voice call in the wireless network. In step 802, the mobile terminal detects the EPSFB triggered by the wireless network. In step 803, the mobile terminal recognizes one or more EPSFB states according to the result of step 802 or the indicator of the network. In step 804, the mobile terminal transmits one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB statuses.

Although the present invention has been described in conjunction with certain specific embodiments for illustrative purposes, the present invention is not limited thereto. Therefore, without departing from the scope of the present invention as set forth in the scope of the patent application, various modifications, adjustments and combinations of various features can be made to the described embodiments.

100: wireless network 101: eNB 102: gNB 103, 104: UE 106:5GC 107:EPC 108: IMS network 126, 136, 156: antenna 111, 113, 116: Uplink 112, 114, 117: Downlink 123, 133, 135, 137, 153: transceiver 122, 132, 152: processor 12, 131, 151: memory 124, 138, 154: program instructions and data 191: Mobile Terminal (MT) 192: Terminal Equipment (TE) 193: EPSFB status module 125, 155: EPSFB module 201: UE 211: MT 202: 5G radio access station/gNB 203: 4G / LTE base station / eNB 204: Network entity 212: upper layer 221~223, 280~283, 231~232: steps 301: UE 302: NG-RAN 303: E-TRAN 304: AMF 305: MME 306: SGW 307: PGW/ SMF/ UPF 308: IMS 311~318, 321, 326: steps 400: UE 401, 600: TE 402: TA 403, 700: MT 601, 701: processor 602, 702: memory 603, 703: Program instructions and data 610, 710: Protocol stack 620: System Control Module 706: Antenna 704: RF transceiver module 705: Baseband Module 720: System Module 801~804: steps

The accompanying drawings are included to provide a further understanding of the present invention, and the accompanying drawings are incorporated in this specification and constitute a part of this specification. The drawings illustrate embodiments of the present invention, and together with the description serve to explain the principle of the present invention. In the attached picture: Figure 1 illustrates an exemplary wireless network and user equipment according to a novel aspect. Figure 2 illustrates an exemplary block diagram of a mobile terminal reporting EPSFB status according to an embodiment of the present invention. Figure 3 illustrates an example diagram of EPSFB for IMS voice when the EPSFB status indication is sent to the upper layer according to an embodiment of the present invention. Figure 4 illustrates a simplified block diagram of the architecture of a user equipment UE according to an embodiment of the present invention. The user equipment UE includes a terminal device (TE 401) and a mobile terminal (MT 403) through a terminal adapter (TA 402) interface. Figure 5 illustrates an exemplary table of AT commands for EPSFB status according to an embodiment of the present invention. Figure 6 illustrates a simplified block diagram of a terminal device (TE 600) with an application layer that receives EPSFB status from an MT according to an embodiment of the present invention. Fig. 7 illustrates a simplified block diagram of a mobile terminal (MT 700) transmitting EPSFB status to an upper layer according to an embodiment of the present invention. Fig. 8 illustrates an exemplary flowchart for the mobile terminal to detect the EPSFB status indication and send it to the upper layer according to an embodiment of the present invention.

801~804: steps

Claims (18)

A voice call method, including: initiating a 5G voice call in a wireless network by a mobile terminal; Detecting an evolved packet system fallback (EPSFB) triggered by the wireless network; Identify one or more EPSFB states; and According to the identified one or more EPSFB statuses, one or more EPSFB status indicators are sent to at least one upper layer. According to the voice call method described in item 1 of the scope of patent application, the EPSFB is a redirection process or a handover process. For the voice call method described in item 1 of the scope of patent application, the EPSFB status indicator includes: a redirection to an evolved packet system (evolved packet system, EPS) start indicator, a switch to an EPS start indicator, and a redirection To the EPS failure indicator, switch to the EPS failure indicator, redirect to the EPS success indicator, and switch to the EPS success indicator. The voice call method according to the first item of the scope of patent application, wherein the mobile terminal uses an AT command to send the one or more EPSFB status indicators. The voice call method according to item 4 of the scope of patent application, wherein the AT command includes one or more parameters, and the one or more parameters include EPSFB status field, EPSFB type field, and report field. The voice call method described in item 5 of the scope of patent application, wherein the AT command sets the value of the report field to 1, so that the EPSFB unsolicited status report is sent to the upper layer. The voice call method according to item 5 of the scope of patent application, wherein the EPSFB status field indicates the EPSFB status, and the EPSFB status includes: starting from the 5G system to the EPS rollback, and from the 5G system to the EPS rollback successfully, And the fallback from the 5G system to the EPS failed. The voice call method according to item 5 of the scope of patent application, wherein the EPSFB type field indicates the EPSFB type, and the EPSFB type includes: handover and redirection. The voice call method as described in item 1 of the scope of the patent application, wherein when one or more disabling instructions are received, sending one or more EPSFB status indicators is prohibited. A mobile terminal, including: The network interface circuit is used to initiate 5G voice calls in the wireless network; A detector circuit for detecting an evolved packet system fallback (EPSFB) triggered by the wireless network; Status circuit for identifying one or more EPSFB status; and The reporting circuit is configured to send one or more EPSFB status indicators to at least one upper layer based on the identified one or more EPSFB statuses. The mobile terminal according to item 10 of the scope of patent application, wherein the EPSFB is a redirection process or a handover process. The mobile terminal according to item 10 of the scope of patent application, wherein the EPSFB status indicator includes: redirect to EPS start indicator, switch to EPS start indicator, redirect to EPS failure indicator, and switch to EPS failure Indicator, redirect to EPS success indicator; and switch to EPS success indicator. The mobile terminal according to claim 10, wherein the mobile terminal uses an AT command to send the one or more EPSFB status indicators. The mobile terminal according to item 13 of the scope of patent application, wherein the AT command is a new EPSFB status AT command including one or more parameters, and the one or more parameters include EPSFB status field and EPSFB type field Bits and report fields. The mobile terminal according to item 14 of the scope of patent application, wherein the EPSFB status command sets the value of the report field to 1, so that the EPSFB unsolicited status report is sent to the upper layer. The mobile terminal according to item 14 of the scope of patent application, wherein the EPSFB status field indicates the EPSFB status, and the EPSFB status includes: starting from the 5G system to the EPS rollback, from the 5G system to the EPS rollback successfully, and The fallback from the 5G system to the EPS failed. The mobile terminal according to item 14 of the scope of patent application, wherein the EPSFB type field indicates the EPSFB type, and the EPSFB type includes: handover and redirection. The mobile terminal according to item 10 of the scope of patent application, wherein after receiving one or more disabling instructions, it is forbidden to send one or more EPSFB status indicators.

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